This work showd that of 62 chemicals which have been reported as insect defense substances, 32 chemicals have more and less antifungal activites agaist 7 species of common fungi which were cultured in an agar medium. The most effective chemicals were aristrochic acid as defense substance of swallowtail butterfly larvae and benzoquinones of tenebrionid or carabid beetles, but most of aliphatic hydrocarbones were not or less active. And also larvral extracts with organic solvents of a lady bug, Rodolia limbata which have defensive secretions against their predetory enemies, were observed to inhibit growth of these fungi. But no prominent antifungal activies were found in larval extracts of Conogethes punctiferalis, Musca domestica and Pascothea hiralis, which have not been known their defensive secretions. However, hexane extracts of these three insects were slightly active agaist 6 species of fungi tested, suggesting a possibility that these insects also have some chemical agents for defensing fungal attack.
These results were strongly suggestive in that insect defense chemicals may be effective agaist environmental microorganisms as a natural enemy of insects.